Single-electron detachment (SED) cross-sections for Cr- and Fe- in collisions with He have been obtained in the energy region of 10-30 keV for the first time. In the present energy range the magnitude of the Cr-+He SED cross-sections is close to that of Fe- + He, although the electron affinity of Fe- (0.16eV) and Cr- (0.668 eV)are different. It is found that the cross-sections for Cr- and Fe- in collisions with He exhibit nearly the same dependence on anions impact velocity.